The present invention relates to electrical interconnection of multi-conductor cables for high-frequency signal transmission, and to economically produced connectors of minimal size for accomplishing such interconnection.
Electrical cables for high-frequency signal transmission may contain many conductors, either as single unshielded conductors, or coaxial conductor pairs, with these conductors arranged in dense patterns such as concentric generally circular layers of conductors or coaxial pairs. Such cables may have more than one thousand of such conductors or conductor pairs. It is desirable to interconnect such multi-conductor cables with a maximum contact density, in order to provide the smallest practical connector size, so that the connectors do not make otherwise convenient cables clumsy to use or cause significant problems related to conductor impedances. Reliable, yet conveniently small connectors for multi-conductor cables are important, for example, in such applications as the provision of electrical connections between signal processing and display portions of medical electronic equipment and other portions of such medical electronic equipment, such as in connecting cables to sensor heads which must be easily movable about the body of a patient. Because of the large number of conductors to be connected it is also desirable for connection of each separate conductor to require only a very small force, so that the total force required for a connection is not too great.
Another factor in the construction of such multi-conductor cable connectors is that the connectors must not provide avenues for significant electrical signal interference among the various conductors of the cables being connected.
It is also important to maintain a controlled impedance through such cable connectors, and for the connectors to be durable enough to withstand repeated connection and disconnection while still providing reliable electrical connection for each of the many conductors of the cable being connected.
Commonly used pin-and-socket connectors for multi-conductor cables are either undesirably large or else very costly to produce. Because of their size, large pin-and-socket connectors may present a problem of impedance mismatching in high-frequency signal transmission through cables connected using such connectors. Also, pin-and-socket connectors often incur damage while being mated or separated, since it is easy to bend individual pins or sockets out of alignment, making it difficult or impossible to achieve electrical interconnection.
Multi-conductor connectors have previously included bodies defining arrayed openings to receive individual conductors, as defined in Hardy, et al., U.S. Pat. No. 4,875,870.
A block holding conductors and respective sockets in a rectangular array as part of a matched-impedance connector for joining round cable to ribbon cable is shown in Tarver U.S. Pat. No. 3,573,704.
Reardon, II, deceased, et al. U.S. Pat. No. 4,125,310 discloses a connector in which raised buttons on mating wafers provide electrical interconnection between ribbon-type cables, but there is no disclosure of how such a connector could be used practically for connecting cables with as many conductors as some cables commonly include.
MacKay U.S. Pat. Nos. 4,862,588 and 4,991,290 disclose a flexible interconnect for providing electrical connection between stacks of electronic components, but do not disclose how such an interconnect could be used for high density connection of the conductors of a multi-conductor cable.
Munro U.S. Pat. No. 3,852,878 discloses a resilient connector with high contact point density, but does not show how such a connector could be used to interconnect cables including large numbers of conductors.
British Patent No. 472,159 discloses contacts formed of precious metal wire, but does not disclose how such contacts could be provided in a high contact density as part of a connector for multi-conductor cables.
Darrow et al. U.S. Pat. No. 4,434,134 discloses the use of a substrate defining holes to receive the respective conductors of a multi-conductor cable, and connector pins cast precisely on the opposite side of the substrate in an aligned array.
Polonio U.S. Pat. No. 4,885,126 discloses the use of gold or conductive elastomeric material in an array having a high contact density, on the underside of a substrate carrying an integrated circuit chip, to connect the chip to a printed circuit on a second substrate, but there is no disclosure of how a suitable connector of similar contact density could be provided for the conductors of a multi-conductor cable.
While it is well known to form conductors extending between buried wires in a multi-layer circuit board and contact pads on the exterior surface of the circuit board by electroplating or similarly depositing conductive material in laser-formed holes, the prior art has not taught how to use such techniques for interconnecting a large number of conductors to contacts arrayed on a surface extending generally perpendicular to the length of the conductors, as in attaching a connector to a multi-conductor cable.
What is needed, then, is an improved connector and an economical method for making such a connector, for reliably and repeatably connecting and disconnecting cables containing a large number of small, closely-spaced, individual electrical conductors without requiring a large amount of force to effect connection or disconnection, and without causing unacceptable impedance changes.